The present invention relates to inflatable protective cushions, and more specifically relates to a cushion formed by the highly efficient continuous winding of yarn. The cushion is particularly useful in the frontal or side protection of occupants in a transportation vehicle, such as an automotive vehicle, railroad, car, airplane, or the like. A process for forming the cushion and an optimum shape for the cushion according to the present invention are also provided.
Inflatable protective cushions used in passenger vehicles are a component of relatively complex passive restraint systems. The main elements of these systems are: an impact sensing system, an ignition system, a propellant material, an attachment device, a system enclosure, and an inflatable protective cushion. Upon sensing an impact, the propellant is ignited causing an explosive release of gases filling the cushion to a deployed state which can absorb the impact of the forward movement of a body and dissipate its energy by means of rapid venting of the gas. The entire sequence of events usually occurs within about 30 milliseconds. In the undeployed state, the cushion is most commonly stored in or near the steering column, the dashboard, in a door panel, or in the back of a front seat placing the cushion in close proximity to the person or object it is to protect.
Inflatable cushion systems commonly referred to as airbag systems have been used in the past to protect both the operator of the vehicle and passengers. Systems for the protection of the vehicle operator have typically been mounted in the steering column of the vehicle and have utilized cushion constructions directly deployable towards the driver. These driver-side cushions are typically of a relatively simple sewn configuration. Typically, traditional driver""s side inflatable cushions have been formed by sewing together two circular pieces of coated fabric made of nylon or polyester yarn.
Although such sewn products have generally performed quite adequately, they nonetheless have some inherent limitations. First, the sewn seam is generally applied or at least inspected manually. As will be appreciated, this is a relatively time consuming process which tends to increase manufacturing costs. Second, circular and elliptical cushions formed by sewing around the perimeter are prone to wrinkles which may result in high and low stress concentrations thereby reducing the maximum inflation pressure which can be maintained at the seam. Third, the introduction of a sewn seam necessarily gives rise to small openings for the sewing threads. These openings tend to act as an escape path for the inflation gases within the airbag which may lead to seam slippage or so called xe2x80x9ccombingxe2x80x9d of the seam thereby giving rise to a potential mechanism for failure. Fourth, even after the two disk shaped components are sewn together, the area surrounding the gas introduction port (i.e. the mouth) must generally be reinforced with additional layers of fabric referred to as doublers so as to control the large forces applied in this area during an inflation event. As will be appreciated, the addition of these doublers gives rise to additional manual processing and the need for additional fabric. Finally, the use of substantially circular shapes may result in substantial material waste during manufacturing due to the inherent inability of the manufacturer to cut disk patterns in close-packed spacing arrangement.
Various alternative sewn constructions have been proposed such as those disclosed in U.S. Pat. No. 5,482,317 to Nelsen et al; U.S. Pat. No. 5,520,416 to Bishop; U.S. Pat. No. 5,454,594 to Krickl; U.S. Pat. No. 5,423,273 to Hawthorn et al; U.S. Pat. No. 5,316,337 to Yamaji et al; U.S. Pat. No. 5,310,216 to Wehner et al; U.S. Pat. No. 5,090,729 to Watanabe; U.S. Pat. No. 5,087,071 to Wallner et al.; U.S. Pat. No. 4,944,529 to Buckhaus; and U.S. Pat. No. 3,792,873 to Buchner (all incorporated herein by reference). However, these constructions each rely on some seaming of precut fabric panels and thus exhibit some if not all of the limitations outlined above.
The manufacture of airbag cushions by means of winding yarns and tape-like materials around a mandrel has been proposed in several publications including Japan Kokai Patent document 3-227751 in the name of Kanuma and Japan Kokai Patent document 3-276845 in the name of Ogami et al. (both incorporated herein by reference).
While these referenced publications recognize many of the limitations inherent in traditional sewn airbags, and have broadly proposed the use of winding technology as a means to avoid those limitations, they nonetheless fail to provide a highly efficient practice for the proper distribution of yarn. Rather, the prior art in this area has relied generally upon the winding of broad, tape like structures or of a relatively large number of parallel yarns to achieve the substantially complete coverage of the cushion surface area. The prior art also fails to teach the ability to preferentially distribute yarns in the area surrounding the inlet opening so as to provide additional support in this area thereby substantially reducing or eliminating the need for the application of an additional reinforcement in this region.
The airbag or cushion according to at least one embodiment the present invention is formed from yarn which is substantially evenly distributed across the face of the cushion thereby avoiding the accumulation of yarn and the ultimate development of a nodule of undue thickness at the center of the cushion where impact with an occupant is likely to occur. In addition, the yarn is disposed in such a manner that a thickened ring of yarn is built up around the inflation opening thereby enhancing the strength of the cushion at the very location where reinforcement is generally required. The yarn, airbag and/or method according to the present invention provides a useful advancement over the present art.
In view of the foregoing, there is provided an improved yarn, fabric airbag and/or method. One object of the present invention is to provide an inflatable restraint made of yarn which possesses an elongation at break of at least about 14.6% when tested according to ASTM Standard Test Method D 2256-97, published by American Society of Testing Materials, 100 Barr Harbor Drive, West Conshohocken, Pa. 19428, and/or possesses a breaking toughness of at least about 0.4 grams per denier where the breaking toughness is defined as the energy to break divided by the product of the denier and the sample length, and/or a tenacity of less than about 10.0 gm/den (gpd).
Another object of the present invention is to provide an inflatable restraint made of yarn which possesses an elongation at break of more than 30% when tested according to ASTM Standard Test Method D 2256-97, published by American Society of Testing Materials, 100 Barr Harbor Drive, West Conshohocken, Pa. 19428, and/or possesses a breaking toughness of more than 1.0 gram per denier where the breaking toughness is defined as the energy to break divided by the product of the denier and the sample length. Further, the inventive yarn may have a tenacity of less than 4.0 gm/den (gpd).
Another object of the invention is to provide an inflatable restraint which can survive the stresses imposed upon it during a rapid inflation, while using a minimum amount of reinforcing yarn.
A still further object of the invention is to make airbags using a winding method using high elongation and/or high toughness yarns.
It is a general object of the present invention to provide an easily manufactured seamless airbag cushion.
It is a more particular object of the invention to provide a seamless airbag cushion formed by the winding of yarn about a removable mandrel such that the yarn is substantially evenly distributed across the face of the cushion.
It is a further object of the present invention to provide a seamless airbag cushion formed by the winding of yarn about a removable mandrel such that the yarn is disposed preferentially across the back of the cushion in the area surrounding the inlet port so as to form a localized region of enhanced thickness to provide additional strength in that region surrounding the inlet port.
It is a further potential object of the present invention to provide a seamless airbag cushion formed by the winding of yarn about a removable rotating mandrel wherein the cushion includes a flexible permeability blocking layer of material holding the yarn in place.
An additional object of the invention is to provide a low cost inflatable protective cushion of simple and structurally efficient design with a shape and construction that optimizes the cushion""s ability to withstand inflation pressure and impact when deployed.
It is a preferred feature of the present invention to provide a seamless airbag cushion formed by the winding of a yarn in a continuous fashion around a generally spheroidal rotating mandrel while systematically shifting the angle of placement of the yarn with respect to the axis of rotation of the mandrel about a point near the mouth of the bag structure being formed such that a localized region of enhanced thickness is formed around the mouth opening.
It is yet a further potentially preferred feature of the present invention to provide a seamless airbag cushion formed by the winding of a yarn in a continuous fashion around a generally spheroidal rotating mandrel having a shape substantially similar to the desired shape of the finished cushion wherein the ratio of the depth of the cushion to its equatorial diameter is about 0.5 to 0.7.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the written description and claims as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.